This invention relates to a fail safe when an abnormal state occurs in a sensor in an electronic control system of an internal combustion engine.
When an abnormal state occurs in a sensor in general, normally an operation for coping with the sensor abnormal state in which an abnormal state is discriminated by detecting that a detected value exceeds a limit value and an operation of the system is stopped or the operation is continued in reference to the fixed limit value in place of the detected value by the sensor is carried out.
However, the stopping in operation of one electronic control system of the internal combustion engine corresponds in general to the stopping in operation of the internal combustion engine and it is not efficient to stop the operation of the internal combustion engine due to the cause of abnormal state in one sensor.
Further, even if the operation of the internal combustion engine is continued at the fixed limited value, it is sometimes happened that an abnormal state in operation occurs.
In particular, in the case that an abnormal state occurs in a sensor for detecting a temperature related to a temperature of the engine, such as a water temperature sensor for detecting the engine water temperature for example, the sensor shows a lower value irrespective of the fact that the temperature of the engine is actually and substantially high during warming of the engine, and when the operation is controlled in response to the detected low temperature, the rotational speed of the engine is increased more than that required and then a so-called blowing-up of the engine speed occurs.